To dose or defile someone's drink, food, etc. Specifically, what waiters secretly do to your food if you're rude or disgusting. The origin is from Alex Haley's "Roots" where ex-slave "Kizzy" (played by Leslie Uggams) spits into the tin cup of her ex-massa (played by Sandy Duncan) before "fetching" her water.

Putting the kizzy or spitting in the drinks of rude restaurant customers.